The field of the disclosure relates generally to components having an internal passage defined therein, and more particularly to forming interior walls that define the internal passages using a plurality of materials.
Some components require an internal passage to be defined therein, for example, in order to perform an intended function. For example, but not by way of limitation, some components, such as hot gas path components of gas turbines, are subjected to high temperatures. At least some such components have internal passages defined therein to receive a flow of a cooling fluid, such that the components are better able to withstand the high temperatures. For another example, but not by way of limitation, some components are subjected to friction at an interface with another component. At least some such components have internal passages defined therein to receive a flow of a lubricant to facilitate reducing the friction.
At least some known components having an internal passage defined therein are formed in a mold, with a core of ceramic material extending within the mold cavity at a location selected for the internal passage. After a molten metal alloy is introduced into the mold cavity around the ceramic core and cooled to form the component, the ceramic core is removed, such as by chemical leaching, to form the internal passage. Alternatively or additionally, at least some known components having an internal passage defined therein are initially formed without the internal passage, and the internal passage is formed in a subsequent process. For example, at least some known internal passages are formed by drilling the passage into the component, such as, but not limited to, using an electrochemical drilling process. In each case, the interior wall that defines the internal passage is defined by the metal alloy used to form the component. Thus, if the interior wall defines, for example, a stress concentration at a particular point, the metal alloy used to cast the entire component must be chosen to satisfy the relatively higher strength needs at that particular point, potentially increasing a cost of the component.
In addition, at least some known components having an internal passage defined therein exhibit improved performance of the intended function after a coating is applied to the interior wall. However, such coatings can be difficult or cost-prohibitive to apply completely and/or evenly to certain internal passageways, such as, but not limited to, internal passageways characterized by a high degree of nonlinearity, a complex cross-section, and/or a large length-to-diameter ratio.